1. Field of the Invention
The present invention relates to a device for detecting an average output current of a power converter and a method for detecting an average output current of a power converter, and particularly to a device and a method that can get dynamic information corresponding to the average output current of a secondary side of the power converter in time.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram illustrating a power converter 100 according to the prior art, and FIG. 2 is a diagram illustrating a gate control signal GCS, a current IP flowing through a primary side PRI of the power converter 100 when a secondary side of the power converter 100 is coupled to a heavy load, and the current IP flowing through the primary side PRI of the power converter 100 when the secondary side of the power converter 100 is coupled to a light load. As shown in FIG. 1, the controller can detect the current IP flowing through the primary side PRI through a current sensing pin CSP, and generate the gate control signal GCS according to the current IP and a detection voltage VD generated by a detection resistor RS. Then, the controller can transmit the gate control signal GCS through a gate pin GATE to a power switch 102 of the primary side PRI of the power converter 100 to control turning-on and turning-off of the power switch 102.
As shown in FIG. 2, the power converter 100 can calculate output power POUTDCM when the secondary side of the power converter 100 is coupled to the light load and output power POUTCCM when the secondary side of the power converter 100 is coupled to the heavy load respectively according to a principle of conservation of energy, equation (1), and equation (2):
                    POUTDCM        =                              η            ×            PIN                    =                      η            ×                          1              2                        ×            LP            ×                          IPP              2                        ×                          1              T                                                          (        1        )                                POUTCCM        =                              η            ×            PIN                    =                      η            ×                          1              2                        ×            LP            ×                                          (                                  IPP                  -                  IPL                                )                            2                        ×                          1              T                                                          (        2        )            
As shown in equation (1), η is a constant, PIN is input power of the primary side PRI of the power converter 100, LP is an inductor of the primary side PRI of the power converter 100, IPP is a maximum value of the current IP flowing through the primary side PRI during the enabled gate control signal GCS, and T is a period of the gate control signal GCS. As shown in equation (2), IPL is a minimum value of the current IP flowing through the primary side PRI during the enabled gate control signal GCS.
As shown in equation (1) and equation (2), because the output power POUTDCM and the output power POUTCCM of the power converter 100 can be influenced by the inductor LP of the primary side PRI of the power converter 100 and the period T of the gate control signal GCS, accuracy of the output power POUTDCM and the output power POUTCCM of the power converter 100 is lower.